Amateur Detective Myrtle Hardcastle must solve the mystery of a long-lost heiress and track down a possible murderer lurking in the halls of the Royal Swinburne Hospital before her father, a patient there, becomes the killer's next victim in Book 4 of the Edgar Award-winning mystery series.

When a mysterious girl attempts to stake her claim to the Snowcroft family fortune, Myrtle Hardcastle's father, a lawyer, is asked to help prove - or disprove - the girl's identity. Is this truly Ethel Snowcroft, believed to be lost at sea with her parents, or a con artist chasing a windfall? Mr. Hardcastle's pursuit of the case takes a detour when he's hospitalized for a tonsillectomy - only to witness a murder. Or does he? With no body at the scene, Myrtle and her governess, Miss Judson, fear the so-called murder was a feverish delusion - until a critical piece of evidence appears.

But where's the victim? And who at the hospital could be harboring murderous intent? Myrtle is determined to find out before the killer comes after her father.
With stakes this high, her sleuthing has put Myrtle, her family, and the patients and staff at the Royal Swinburne Hospital In Myrtle Peril.